Pressure responsive transfer system and process of making



Nov. 12, 1968 H. WINZER 3,410,712

PRESSURE RESPONSIVE TRANSFER SYSTEM AND PROCESS OF MAKING Filed Oct. 19, 1965 7 W/ FIG. I

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HERMAN/V W/MZEQ United States Patent 01 lice 3,410,712 Patented Nov. 12, 1968 3,410,712 PRESSURE RESPONSIVE TRANSFER SYSTEM AND PROCESS OF MAKING Hermann Winzer, Duren, Rhineland, Germany, assignor to Renker-Belipa G.m.b.H., Lendersdorf-Krauthausen,

Germany Filed Oct. 19, 1965, Ser. No. 497,670 16 Claims. (Cl. 117--36.3)

This invention generally relates to writing and manifold material and is particularly directed to a pressure sensitive transfer or duplicating system which permits the transfer of writing, symbols, markings, and the like (hereinafter collectively being referred to as writing) without the use of ordinary carbon papers. The invention is also concerned with a method of producing the novel transfer system.

Conventional carbon and other such transfer papers comprise a wax-containing color layer which is normally covered by a further wax coat. These conventional carbon or transfer papers suffer from the serious disadvantage that they :are not sufiiciently clean on handling. Soiling of the hands and clothing of a user cannot usually be avoided even if extreme care is taken. Due to the wax components contained in the color and/ or coating layer of such conventional carbon papers, the copies produced moreover tend to smear and smudge, a disadvantage which becomes particularly pronounced upon frequent handling of the copies. It should alsobe considered that the interposition of customary carbon papers between paper sheets considerably increases the total thickness of the set of sheets, a disadvantage which of course limits the number of copies which can be produced since ordinary inscribing or writing pressure is not sufficient to cause the production of many legible copies. This disadvantage makes itself particularly felt in the number of copies which can be produced with such customary carbon papers in a typewriter.

Accordingiy it is a primary object of the present invention to overcome the disadvantages of the prior art carbon papers as referred to.

Generally it is an object of this invention to improve on the art of transfer or duplicating materials and the methods for their preparation, as presently practiced.

Briefly, and in accordance with this invention, the inventive pressure-responsive transfer system comprises a carrier member such as, for example, a paper sheet. One of the surfaces of the paper sheet, to wit, the surface from which writing is to be transferred upon the application of writing pressure, is provided with a plurality of depressions. Pigment particles of smaller size than the depressions are embedded or lodged within the latter. These pigment particles are enveloped by a thin elastic skin or coat which is formed from one or several vinyl polymers. The vinyl polymers may contain plasticizers. The color transfer from this color-enriched carrier is induced by a separate color transfer inducing layer which is arranged between the surface of the paper carrier which has the pigment-filled depression and a receiving sheet, to wit, a sheet which is arranged for receiving the writing. This color transfer inducing layer exhibits sufficient adhesive characteristics both with respect to the color carrier and also in respect to the receiving sheet, so as to be capable to cause the transfer of pigment particles from the color carrier to the receiving sheet at those areas which are subjected to writing pressure.

In accordance with the invention, the type of the pigment composition described in the following is chosen so that penetration of color to the opposite surface of the carrier does not take place after lodging the pigment particles on a carrier, to wit e.g. a paper sheet. In other words, the pigment particles are retained within the depressions on one face of the carrier and do not break through to the opposite face thereof. Consequently, the inventive transfer sheets can be prepared so that one face of the sheets acts as a writing receiving surface while the opposite face is constructed as a transfer surface which transfers writing to a receiving surface of a sheet arranged in subjacent position. The total thickness of sets of paper sheets can be significantly reduced, and all the sheets of such a set will produce clearly legible copies with sharp and smudge-free contours. While customary carbon papers have to be removed from the paper sets after the copies have been produced, the inventive transfer system may thus be arranged so that the transfer-producing layers form an integral part of the copies.

The inventive transfer system produces copies of superior legibility and sharpness and the copies are surprisingly smearand smudge-resistant. Moreover, a large number of copies can simultaneously be produced.

As previously set forth, paper is the preferred carrier material, although sheets of any suitable organic or inorganic material could be used. In a preferred embodiment, paper sheets of a thickness of 20 to p. are employed. That surface of the paper sheet from which the color transfer takes place is not plane but has a large number of depressions which are spaced from each other by distances of about 1 to 50;. The outer boundaries of these depressions are formed by protuberances or ridges in the paper surface, for example, formed by paper fibers which extend inthe surface of the paper carrier with a width of preferably up to 50a. The depressions have a depth of at least about 10 but not more than at the most about 60% of the thickness of the paper carrier.

The pigment particles are embedded or lodged within these depressions. These pigment particles thus form the color material for the transfer of the writing.

In accordance with the invention, pigment particles are .used whose diameter is smaller than the depressions of the carrier. For this purpose the pigment is ground into a particle size sufficiently fine so as to be smaller than the depressions referred to. The pigment particles are mixed with a binder in the form of elastic vinyl polymers and a liquid which acts as solvent for the polymers but which does not dissolve the pigment. The pigment particles are uniformly distributed throughout this liquid phase. The amount of elastic vinyl polymers in the mixture referred to is chosen so that it advantageously corresponds to 15 to 25% by weight, calculated on the weight of the pigment particles.

In this manner each pigment particle is coated with a thin elastic resin skin or coat. It is also within the scope of this invention to grind the pigment to the necessary fineness after it has been incorporated into the liquid which contains the binding agent. Particularly favorable results are obtained if the pigment is admixed with a small amount of silicic acid particularly in colloidal form.

The pigment composition thus prepared is applied to.

the face of the carrier which is provided with the depressions. Excess of the pigment composition is thereupon removed by means of a wiper or doctor blade which bears directly on the protuberances on the paper surface. In this manner, the pigment particles are removed from the protuberances and are solely lodged within the depressions. The protuberances thus act merely as separating ridges between the individual depressions. The pigment-enriched paper carrier is thereupon dried.

So-called color lacquers, to wit, organic dye stuffs deposited on inorganic pigments are preferred pigments for the purposes of this invention. This is so since such color lacquers are insoluble in solvents which customarily are used for dissolving vinyl polymers, such as methanol and water. Therefore, any danger of penetration of the color to the opposite face of the paper carrier is avoided even if very thin paper carriers are employed. However, other color substances are also suitable such as, for example, phthalocyanine colors and inorganic pigments as, for ex ample, ultramarine or organic or inorganic black pigments.

Various vinyl polymers may be used for the inventive purposes. Particularly favorable results are obtained with vinyl acetate having an average molecular weight of about 20,000 to 50,000. However, also vinyl copolymers can be employed as, for example, vinyl chloride-vinyl acetate copolymers, wherein the ratio of vinyl chloride to vinyl acetate is between about 80-90:l020% with a K value of 40 to 65. Polyvinyl alcohols with about 12% of acetyl groups are also suitable.

It will be noted that the ratio of binder, to wit, vinyl polymer, to pigment is not the usual one since customarily in color lacquers the binder moiety by far exceeds the color moiety. Rather in accordance with the invention only about 15 to 25% by weight of binder, calculated on the pigment moiety, are used. This ratio is characteristic for the color preparations to be used in accordance with this invention and it constitutes an important feature of the invention. This is so because an insuflicient amount of vinyl polymer would cause but an incomplete enveloping of the pigment particles which could result in peeling of the preparation. By contrast, if large amounts of binder are used, the pigment particles tend to become bonded to the paper carrier to such an extent that the desired transfer upon application of writing pressure is impeded if not prevented. The indicated percentage ratio of 15 to 25% of binder has proved to be entirely satisfactory.

The inventive procedure assures a bonding of the color particles to the carrier to such an extent that rubbing off, smearing, or other undesired or untimely removal of the pigment color from the carrier is effectively prevented, while on the other hand removal of the color particles by means of the adhesive transfer-inducing layer is readily accomplished upon application of writing pressure.

In accordance with a further feature of the invention, the transfer inducing layer is in the fomi of a gel, to wit, a two-phase system consisting of a network of solid particles in which liquid is held. In preparing such a gel in accordance with the invention use is made of one or several polyethylenes with an average molecular weight of about 1500 to 2000. The polyethylenes are moreover defined by a melting point of about 80 to 110 C., a viscosity at 140 C. of about 100 to 250 cps, a specific weight of about 0.92 and a penetration hardness of about 0.2 to 4.0 as determined on 100 grams, for 5 secOnds at 77 F. in accordance with ASTMD l32l57 T.

The said gel is prepared by dissolving 2 to 7 parts by Weight of the previously defined polyethylene or a mix-- ture of such polyethylenes in 93 to 98 parts by weight of a suitable solvent. Preferred solvents are liquid aliphatic hydrocarbons having 4 through 12 carbon atoms or liquid aliphatic chlorinated hydrocarbons with 1 to 6 carbon atoms. The dissolution is effected at elevated temperature up to the boiling point of the solvent, whereupon the solution is cooled to about 20 C. A portion of the polyethylene precipitates in this manner in the form of gel, the liquid moiety of which is a solution of the remaining portion of the polyethylene in the used solvent. This liquid polyethylene solution moiety of the gel at 20 C. should contain polyethylene in dissolved state amounting to at least 0.7 and at most 1.7% by weight of the solution, whereas the greater amount of the polyethylene is the solid component of the gel. The particular polyethylene types, the quantity ratio of mixed polyethylene types and the suitable solvent, any within the definitions given hereinabove, should be chosen so as to obtain a preparation in which the indicated polyethylene content in the liquid moiety of the gel, to wit, 0.7 to 1.7% by weight at 20 C., is realized. From a practical point of view, solution tests may first be carried out in order to determine the proper choice. Such a test may be performed as follows:

About 500 g. of a hot clear solution containing the polyethylene or polyethylene mixture and the solvent in composition and quantity ratio corresponding to the intended production is prepared and then cooled to about 20 C. while stirring. At the end of cooling an opaque mixture is formed due to the gel formation. The viscosity of this mixture strongly increases. The weighed portion of this mixture is then centrifuged at 3000 revolutions per minute for two hours. Dependent on the density of the solvent, the polyethylene gel will collect on top or at the bottom of the centrifuging vessel. The supernatant or subjacent clear solution, as the case may be, is then carefully withdrawn. If the solution is situated below the gel layer, a glass pipe is vertically pushed through the gel layer and into the solution, the bottom opening of the glass pipe being closed by an easily penetrated or ruptured material, such as a foil or cork. The other opening of the glass pipe should project somewhat above the level of the centrifuging vessel. The centrifuging is thereupon continued until the gel, which has been somewhat disturbed by the insertion of the pipe, has again collected on top of the solution and the solution is clear. The closure in the lower opening of the pipe is then removed or ruptured, whereupon the clear solution is sucked through the pipe, for example by an ordinary hollow needle-suction device as, for example, an injection syringe arrangement as used for medical purposes. The content of polyethylene is then gravimetrically determined in the withdrawn solution as dry residue.

With a view to forming the transfer-inducing layer, the hereinabove described polyethylene gel which at 20 C. has a condition fit for the coating procedure, is applied either to that face of the paper carrier whose depressions are filled with the enveloped pigment particles or to one surface of a receiving sheet. The thus coated carrier is carefully dried, for example, by a slightly heated air flow. In this manner is removed the excess solvent from the liquid moiety of the gel. Thus after the drying, a transferinducing layer in the form of an immobilized gel is formed, which is a network of solid polyethylene components in which a residue of at most 10% by weight of liquid solution is retained which, calculated on the amount of this solution moiety, contains between 0.7 to 1.7% by weight of polyethylene in dissolved form.

It should be strongly emphasized that the application of a transfer layer in the form of a solution would not give satisfactory results, since such a solution would penetrate the carrier and make impossible the transfer of the pigment particles because all of these particles thus would be bound fast together and to the support.

The use of the transfer-inducing layer in the form of an immobilized gel has the advantage that the intramolecular liquid of the gel, which contains dissolved portions of the polyethylene, exhibits excellent adhesive characteristics suitable for transfer purposes. The limit values of the dissolved polyethylene in this liquid moiety of the gel should advantageously be within the indicated range of 0.7 to 1.7% by weight at 20 C. in order to obtain the optimum effect of the inventive transfer system. In addition, such transfer-inducing layer has a long shelf life.

As previously set forth, the transfer-inducing layer can be directly coated onto the color containing face of the carrier, whereby the polyethylene layer will be adhesively bonded to said face. However, as stated, the transferinducing layer may instead be applied as surface layer of the receiving sheet. In the latter alternative, the pigment particles which are transferred from the color carrier under pressure, are also lodged in smearand smudgeresistant manner on the receiving sheet.

In the production of sets of sheets, those sheets which are arranged below the first sheet adapted to receive the writing, may be provided on their upper face with the transfer-inducing polyethylene layer and on the rear or opposite face with the coated pigment particles.

In the drawings:

FIG. 1 shows an exploded view of one embodiment of the inventive transfer system in vertical section;

FIG. 2 shows a second embodiment of this system in exploded view;

FIG. 3 shows a transfer sheet suitable for use in sets; and

FIG. 4 is a plan view of a transfer sheet without transfer-inducing layer.

Referring now to the drawings, the transfer system of FIG. 1 comprises a transfer sheet, generally indicated by reference numeral 10, and a receiving sheet 8. The transfer sheet comprises a carrier sheet 1 of paper whose bottom face is provided with a number of depressions 2 which are spaced from each other and which have a depth of about 10 to 60% of the thickness of the paper carrier. The depressions 2 are separated from each other by ridges or protuberances 3 formed by paper fibers extending on the surface of the paper carrier 1. Pigment particles 4, coated with vinyl polymers, are lodged within the depressions 2. The ridges or protuberances 3 are free from any pigment particles. A polyethylene gel layer 7 of the indicated nature is superimposed on the color-containing face of the paper carrier 1. Reference numeral 8 indicates an ordinary paper sheet. During use the transfer sheet 10 is placed on the receiving sheet 8 and upon application of writing pressure the transfer-inducing polyethylene layer 7 will remove pigment particles 4 and lodge them on the receiving sheet 8.

According to the embodiment of FIG. 2, the polyethylene layer 7 is applied to the receiving sheet 8' and not to the color-containing face of the paper carrier 1. The embodiment of FIG. 2 is otherwise the same as that of FIG. 1, the paper carrier 1' having a number of depressions 2' which are separated by ridges 3, coated pigment particles 4 being lodged within the depressions.

FIG. 3 shows an embodiment wherein the transfer sheet 10" contains both a receiving surface and color for transfer purposes. To this end, the paper carrier 1" is, as in the previous embodiments, provided with a number of depre'ssions 2" which accommodate the vinyl polymercoated pigment particles 4". The polyethylene gel layer 7" is applied to the opposite face of the paper carrier 1". This embodiment is particularly suitable for use in sets of sheets for the production of multiple copies. Thus, if the uppermost sheet in the set corresponds to the transfer sheet 10' of FIG. 2, the remaining sheets to be arranged subjacent the top sheet can then suitably be of a construction as shown in FIG. 3. The color transfer from the top sheet which is indicated by the arrow A will pro duce a copy through the presence of the polyethylene layer 7" on the paper carrier 1" while the next copy will be produced on the subjacent sheet as indicated by the arrow B, the pigment particles 4" thus being transferred to the top polyethylene gel layer on the next sheet.

FIG. 4 shows a plan view of a transfer sheet in which the enveloped pigment particles 40 are seen as being EXAMPLE I Preparation Ia for obtaining enveloped pigment particles Parts by weight Alizarin color lacquer 15.0 Silicic acid 0.8 Polyvinyl acetate (average molecular weight 35,000; K value 20) Methanol Total 100.0

Preparation 112 for preparing polyethylene gel Parts by weight Polyethylene (average, molecular weight 2000; melting point 102-106" C.; viscosity at 140 C.: 220 cps.; specific gravity: 0.92; penetration at g., 5 seconds, 77 F.: 0.20.3) Carbon tetrachloride Total 100.0

A paper web was used as carrier. The paper web had a thickness of 40 4. The surface of the paper carrier had numerous depressions of a depth of 10 to 60% of the paper thickness. The individual depressions were spaced from each other by about 1 to 50 and were separated from each other by surface ridges or protuberances. Preparation Ia was applied to the paper web by means of a customary application means. Excess was then wiped off by means of a doctor blade which contacted directly the ridges on the paper surface so that merely the depressions Were filled with the color preparation While the ridges or protuberances remained free.

Preparation Ib was then applied on top of the face of the paper web which had the pigment-filled depressions. Preparation Ib at the time of the application exhibited an immobilized gel forming aggregating condition. This was obtained by heating the application roller used for the application and the tub which contained the preparation, to a temperature at which the polyethylene was completely dissolved, whereupon the solution was cooled until gel formation set in. If necessary, and in order to prevent any penetration of the liquid through or into the carrier, the process may be accelerated by cooling. Any excess of the polyethylene material could be removed, for example, by means of a wiper or doctor blade. The layer was then dried to remove the excess solvent whereupon the coated Web was rolled up. The polyethylene layer is anchored at the pigment particles primarilyby the residue of polyethylene which remains dissolved in the gel. In this case the dissolved portion of polyethylene amounts to about 1.1% by weight of the applied gel. The thus formed transfer-inducing layer had a weight of about 1-5 gram per square meter.

Other application methods, e.g. spraying methods, for applying the transfer inducing layer also yield satisfactory results. In order to obtain uniform distribution and removal of the excess material, air brushes instead of wipers may be used. In any event, however, care should be taken that the polyethylene-containing preparation, which ultimately forms the transfer-inducing layer, is applied sufficiently thin in order to assure uniform application by the application roller. It is also advantageous to mix or 7 agitate the preparation prior to application in order to prevent excessive coagulation of the solid particles.

EXAMPLE II Preparation IIa (color preparation) Parts by weight Ultramarine 15 .0 Silicic acid 0.1

Polyvinyl acetate (average molecular weight 35,000;

K-value 20) 3 .0 Methanol 81.0

Total 100.0

Preparation IIb for obtaining transfer-inducing polyethylene gel layer Parts by weight Polyethylene (average molecular weight 2000, melting point 100-106 C., viscosity at 140 C.: 220 cps., specific weight: 0.92, penetration at 100 g.,

5 seconds, 77 F.: 0.2-0.3) 2.3 Polyethylene (average molecular weight 00, melting point 102106 C., viscosity at 140 C.: 100 cps., specific weight 0.92, penetration at 100 g.,

5 seconds, 77 F.: 1.2-2.0) 1.1

Benzine 110/140 96.6

Total 100.0

A paper web of 60 thickness was used as carrier material. The web had the depression-ridge formations as indicated in Example I. This paper carrier was coated with preparations Hu and Ilb in the same manner as explained in Example I. The residue of polyethylene which remains in dissolved condition in the gel amounted in this example to about 1.2 parts by weight of the total weight of the gel.

EXAMPLE III Preparation Illa (color preparation) Parts by weight Black pigment 15.0 Silicic acid 0.7

Polyvinyl acetate (average molecular weight 3500;

K-value 3.0 Methanol 81.0

Total 100.0

Preparation IIIIJ (polyethylene gel) Parts by weight Polyethylene (average molecular weight 2000, melting point 100-106 C., viscosity at 140 C.: 220 cps., specific weight: 0.92, penetration at 100 g.,

Preparations HM and EU: are applied to a paper carrier of p. thickness in the manner described in connection with Example I. The paper carrier has the surface depressions as previously described. About 1.6 parts by weight of the polyethylene remain in dissolved condition, calculated of a total weight of the polyethylene gel applied to the carrier.

The transfer sheets according to the invention may be used, for example, for telex rolls, bookkeeping rolls, endless forms, sets of forms for typewriters and office duplicating machines, for example Rotaprint machines, Adrema machines, daily summaries for banks, paying-in and out instructions, transfer forms, weighing cards, weight lists,

Cir

stick-on address labels, express cards with a duplicating and stick-on address, consignment notes, police reporting forms, cash register rolls, wage lists and wage accounting systems.

While specific embodiments of the invention have been shown and described in detail to illustrate the application of the inventive principles, it will be understood that the invention may be embodied otherwise without departing from such principles.

What is claimed is:

1. A pressure responsive transfer system for the production of copies, comprising:

(a) a paper carrier having first and second faces and having a thickness of about 20-80a( at least one of said first and second faces defining a plurality of depressions of a depth of about 10-60 percent of the thickness of the paper carrier, said depressions being spaced from each other by distances of about 1-S0a and being separated by protruding areas of said one face;

(b) a plurality of pigment particleslodged within said depressions, said pigment particles being of a smaller size than the size of the depressions, each of said pigment particles being enveloped by a coat of a binding agent comprising an elastic vinyl polymer, said coat constituting about 15-25 percent of the weight of the pigment particles; and

(c) a transfer inducing layer interposed between said one face and a receiving material, said transfer inducing layer having a weight of about 1-5 grams per square meter of layer, said transfer inducing layer comprising an immobilized gel consisting of at least one polyethylene of an average molecular weight of about 1500-2000, a melting point of about -110" C., a viscosity at 140 C. of about 100-250 cps., a specific weight of about 0.92 and a penetration hardness of about 0.2-4.0 as determined with 100 grams for 5 seconds at a temperature of 77 F. according to ASTM-D 1321-57 T in form of a solid network including a solution of said polyethylene in a liquid solvent, said solution amounting to less than 10 percent of the Weight of the solid polyethylene network and containing dissolved polyethylene in an amount of at least 0.7 and at the most 1.7 percent of the weight of the included solution.

2. A system as claimed in claim 1, wherein said pigment particles have a size of at the most about 50 1,.

3. A system as claimed in claim 1, wherein said pigment particles consist of inorganic pigments which are coated with organic dyestutf.

4. A system as claimed in claim 1, wherein said pigment particles are ultramarine particles, phthalocyanine color particles or black pigment particles.

5. A system as claimed in claim 1, wherein said vinyl polymer enveloping said pigment particles consists of polyvinyl acetate having an average molecular weight of between about 20,000 and 50,000.

6. A system as claimed in claim 1, wherein said vinyl polymer enveloping said pigment particles consists of polyvinyl alcohols with an acetyl content of about 12%.

7. A system as claimed in claim 1, wherein said vinyl polymer enveloping said pigment particles is a vinyl chloride-vinyl acetate mixed polymer having a content of vinyl chloride of about 80 to and a vinyl acetate content of about 10 to 20% as well as having a K value of about 40 to 65.

8. A system as claimed in claim 1, wherein the liquid solvent of said polyethylene solution included in the gel essentially consists of a liquid aliphatic hydrocarbon of 6 to 12 carbon atoms or of a liquid aliphatic chlorinated hydrocarbon of 1 to 6 carbon atoms.

9. A system as claimed in claim 1, wherein said transfer-inducing layer is adhesively superimposed onto said one face which contains the coated pigment particles in said depressions.

10. A system as claimed in claim 1, wherein said transfer-inducing layer is applied to said receiving material which is adapted to be placed below said one face of said paper carrier.

11. A pressure responsive transfer sheet comprising:

(a) a carrier having first and second faces and having a thickness of about 20 to 8011., at least one of said faces defining a plurality of depressions of a depth of about to 60% of the thickness of the carrier, said depressions being spaced from each other by distances of about 1 to 50 (b) a plurality of pigment particles lodged within said depressions, said pigment particles being of a smaller size than the size of the depressions, each of said pigment particles being enveloped by a coat of a binding agent comprising an elastic vinyl polymer, said coat constituting about to 25 of the weight of the pigment particles;

(c) a transfer-inducing layer coated onto said one face of said carrier, said transfer-inducing layer comprising an immobilized gel consisting of at least one polyethylene of an average molecular weight of about 1500 to 2000, a melting point of about 80 to 110 C., a viscosity at 140 C. of about 100 to 250 cps, a specific weight of about 0.92 and a penetration hardness of about 0.2-4.0 as determined with 100 grams for 5 seconds at a temperature of 77 F. according to ASTM-D 1321-57 T, which is in the form of a solid network including a solution of said polyethylene in a liquid solvent, said solution amounting to less than 10 percent of the weight of the solid polyethylene network and containing dissolved polyethylene in an amount of at least 0.7 and at the most 1.7 percent of the weight of the included solution.

12. A pressure-responsive transfer system for the production of copies comprising:

(a) a carrier having first and second faces and having a thickness of about to 80a, at least one of said faces defining a plurality of depressions of a depth of about 10 to 60% of the thickness of the carrier, said depressions being spaced from each other by distances of about 1 to 50 lb) a plurality of pigment particles lodged within said depressions, said pigment particles being of a smaller size than the size of the depressions, each of said pigment particles being enveloped by a coat of a binding agent comprising an elastic vinyl polymer, said coat constituting about 15 to by weight of the weight of the pigment particles;

(c) a receiving sheet, said receiving sheet being coated with a transfer-inducing layer, said transfeninducing layer comprising an immobilized gel consisting of at least one polyethylene of an average molecular weight of about 1500-2000, a melting point of about 80-110 C., a viscosity at 140 C. of about 100-250 cps., a specific weight of about 0.92 and a penetration hardness of about 0.2-4.0 as determined with 100 grams for 5 seconds at a temperature of 77 F. according to ASTM-D 1321-57 T, which is in the form of a solid network including a solution of said polyethylene in a liquid solvent, said solution amounting to less than 10 percent of the weight of the solid polyethylene network and containing dissolved polyethylene in an amount of at least 0.7 and at the most 1.7 percent of the Weight of the included solution, said transfer-inducing layer bein-g adapted to be in contact with said one face of said carrier.

13. A process of producing a pressure responsive transfer system, which comprises the combination of the following process steps:

(a) mixing pigment particles of a particle size not exceeding about 50 with about 15-25% by weight, calculated on the weight of the pigment particles, of an elastic vinyl polymer binding agent, said binding agent being dissolved in a solvent which does not dissolve the pigment particles, whereby said pigment particles become enveloped by said binding agent;

(b)(l) dissolving 2-7 parts by weight of polyethylene in 93-98 parts by weight of a liquid hydrocarbon of 4-12 carbon atoms or a chlorinated hydrocarbon of 1-6 carbon atoms, said polyethylene being defined by an average molecular weight of about 1500-2000, a melting point of about -110 C., a viscosity at 140 C. of about -250 cps., a specific weight of about 0.92 and a penetration hardness of about 0.2- 4.0 as determined with 100 grams for 5 seconds at a temperature of 77 F. according to ASTM-D 1321-57 T, said dissolution being effected at a temperature corresponding to about the boiling point of said hydrocarbon, and (2) cooling the solution thus obtained to about 20 C., whereby a polyethylene gel is obtained;

(c)( l) applying the enveloped pigment particles of (a) to one face of a paper carrier having a thickness of about between 20-80,u. and defining a plurality of surface depressions on said face, said depressions being spaced from each other by distances of about 1-50,ll, and being separated by protruding areas of said face, said depressions having a depth of about 10-60% of the thickness of said paper carrier, (2) scraping said one face of said paper carrier to remove enveloped pigment particles from the protruding areas and filling said depressions with enveloped pigment particles and (3) drying the pigment containing paper carrier thus obtained;

(d)(1) applying the gel of (b) to said one face of (c) at a temperature of about 20 C. to obtain a gel layer of about 1-5 grams per square meter and (2) drying the gel layer with a slightly heated air flow, whereby an immobilized gel layer is obtained and thus forming a network of solid aggregates of said polyethylene in which a liquid solution of said polyethylene is held, said solution amounting to less than 10% of the Weight of said solid network and containing the dissolved polyethylene in an amount of at least 0.7 and at the most 1.7% of the weight of this solution.

14. A process of producing a pressure responsive transfer system, Which comprises the combination of the following process steps: preparing a carrier sheet of a thickness of about between 20-80n and having on at least one of its faces a plurality of surface depressions which are spaced from each other by distances of about 1 to 50 said depressions having a depth of about 10 to 60% of the thickness of the carrier, mixing pigment particles of a particle size smaller than the size of said depressions with about 15 to 25% by weight, calculated on the weight of the pigment particles, of an elastic vinyl polymer binding agent, said binding agent being dissolved in a solvent which does not dissolve the pigment particles, whereby the pigment particles become enveloped by said binding agent, filling the enveloped pigment particles into the depressions of said carrier, dissolving 2 to 7 parts by weight of polyethylene in 93 to 98 parts by Weight of a solvent at the boiling temperature of the solvent, said polyethylene being defined by an average molecular weight of about 1500-2000, a melting point of about 80-100 C., a viscosity at C. of about 100-250 cps, a specific weight of about 0.92 and a penetration hardness of about 02-40 as determined with 100 grams for 5 seconds at a temperature of 77 F. according to ASTM-D 1321- 57 T, cooling the solution thus obtained to about 20 C. whereby a polyethylene gel is obtained, applying the gel to said one face of the carrier having the pigmentfilled depressions and drying the gel layer to obtain an immobilized gel layer, to wit, a network of solid aggregates of said polyethylene in which a liquid solution of said polyethylene is held, said solution. amounting to at the most 10% of the weight of said network and containing the dissolved polyethylene in an amount of at least 0.7 and at the most 1.7% of the weight of this solution.

15. A process of producing a pressure responsive transfer system, which comprises a combination of the following process step: preparing a carrier sheet of a thickness of about between 80/L and having on at least one of its faces a plurality of surface depressions which are spaced from each other by distances of about 1 to said depressions having a depth of about 10 to of the thickness of the carrier, mixing pigment particles of a particle size smaller than the size of said depressions with about 15 to 25% by Weight, calculated on the Weight of the pigment particles, of an elastic vinyl polymer binding agent, said binding agent being dissolved in a solvent which does not dissolve the pigment particles, whereby the pigment particles become enveloped by said binding agent, filling the enveloped pigment particles into the depressions of said carrier, dissolving 2 to 7 parts by Weight of polyethylene in 93 to 98 parts by weight of a solvent at the boiling temperature of the solvent, said polyethylene being defined by an average molecular weight of about 1500-2000, a melting point of about 100 C., a viscosity at C. of about 100250 cps., a specific weight of about 0.92 and a penetration hardness of about 0.2-4.0 as determined with 100 grams for 5 seconds at a temperature of 77 F. according to ASTMD 132157 T, cooling the solution thus obtained to about 20 C. whereby a polyethylene gel is obtained, applying the gel to one surface of a receiving sheet and drying the gel layer to obtain an immobilized gel layer, to wit, a network of solid aggregates of said polyethylene in which a liquid solution of said polyethylene is held, said solution amounting to at the most 10% of the weight of said network and containing the dissolved polyethylene in an amount of at least 0.7 and at the most 1.7% of the weight of this solution.

16. A transfer system as claimed in claim 1, wherein said pigment particles are admixed with a minor quantity of silicic acid.

References Cited UNITED STATES PATENTS 3,169,880 2/1965 Strauss 117-36.3 3,203,832 8/1965 Mino 117-36.3 3,226,134 12/1965 Breidthardt 11736.3 3,243,312 3/1966 Schutzmer et al 1l7"36.3 3,256,107 6/1966 Strauss l1736.3 3,294,571 12/1966 Ernst ll7-36.3

MURRAY KATZ, Primary Examiner. 

1. A PRESSURE RESPONSIVE TRANSFER SSTEM FOR THE PRODUCTION OF COPIES, COMPRISING: (A) A PAPER CARRIER HAVING FIRST AND SECOND FACES AND HAVING A THICKNESS OF ABOUT 20-80U(AT LEAST ONE OF SAID FIRST AND SECOND FACES DEFINING A PLURALITY OF DEPRESSIONS OF A DEPTH OF ABOUT 10-60 PERCENT OF THE THICKNESS OF THE PAPER CARRIER, SAID DEPRESSIONS BEING SPACED FROM EACH OTHER BY DISTANCES OF ABOUT 1-50U AND BEING SEPARATED BY PROTRUDING AREAS OF SAID ONE FACE; (B) A PLURALITY OF PIGMENT PARTICLES LODGED WITHIN SAID DEPRESSIONS, SAID PIGMENT PARTICLES BEING OF A SMALLER SIZE THAN THE SIZE OF THE DEPRESSIONS, EACH OF SAID PIGMENT PARTICLES BEING ENVELOPED BY A COAT OF A BINDING AGENT COMPRISING AN ELASTIC VNYL POLYMER, SAID COAT CONSTITUTING ABOUT 15-25 PERCENT OF THE WEIGHT OF THE PIGMENT PARTICLES; AND (C) A TRANSFER INDUCING LAYER INTERPOSED BETWEEN SAID ONE FACE AND A RECEIVING MATERIAL, SAID TRANSFER INDUCING LAYER HAVING A WEIGHT OF ABOUT 1-5 GRAMS PER SQUARE METER OF LAYER, SAID TRANSFER INDUCING LAYER COMPRISING AN IMMOBILIZED GEL CONSISTING OF AT LEAST ONE POLYETHYLENE OF AN AVERAGE MOLECULAR WEIGHT OF ABOUT 1500-2000, A MELTING POINT OF ABOUT 80-110* C., A VISCOSITY AT 140*C. OF ABOUT 100-250 CPS., A SPECIFIC WEIGHT OF ABOUT 0.92 AND A PENETRATION HARDNESS OF ABOUT 0.2-4.0 AS DETERMINED WITH 100 GRAMS FOR 5 SECONDS AT A TEMPERATURE OF 77*F. ACCORDING TO ASTM-D 1321-57 T IN FORM OF A SOLID NETWORK INCLUDING A SOLUTION OF SAID POLYETHYLENE IN A LIQUID SOLVENT, SAID SOLUTION AMOUNTING TO LESS THAN 10 PERCENT OF THE WEIGHT OF THE SOLID POLYETHYLENE NETWORK AND CONTAINING DISSOLVED POLYETHYLENE IN AN AMOUNT OF AT LEAST 0.7 AND AT THE MOST 1.7 PERCENT OF THE WEIGHT OF THE INCLUDED SOLUTION. 